As a device test method, there is a method to provide a semiconductor wafer with a plurality of devices formed thereon to a testing apparatus including a probe card, and test electrical properties of each device in a state where the devices are formed on the wafer. In this method, the test on the electrical properties of each device is carried out by electrically contacting each of a plurality of electrode pads of each device formed on the semiconductor wafer with a plurality of probes installed in the probe card. Through this test, one probe needle mark is formed on each of the plurality of electrode pads of the devices. When all of the probes appropriately electrically contact with their corresponding electrode pads, the test on the electrical properties of the devices can be certainly performed.
However, some of the plurality of probes sometimes cannot accurately contact with the electrode pads, because there is a problem in their installation, or they are deformed with the lapse of time due to the repetitive uses of the probe card. This contact failure causes test failure.
Therefore, in the conventional art, a semiconductor wafer is observed with the naked eye or an image of the semiconductor wafer is obtained by using an image capturing means, such as a CCD camera, and the quality of the probe needle mark formed on a plurality of electrode pads of each device is automatically determined based on the captured image.
However, in the case where an image capturing means, such as a CCD camera is used, as in the conventional art, when the quality of each of marks formed on a plurality of electrode pads is individually determined as a probe needle mark, the determination may be wrong due to the following reasons. For example, when the image capturing means captures an image of a semiconductor wafer, it cannot be accurately recognized as a probe needle mark due to a change in luminance between an electrode pad and a needle mark of a probe. Also, a probe needle mark may be inaccurately determined due to the position of the probe needle mark formed across the edge of an electrode pad. Or, when a cut-off scrap caused by a probe remains in the electrode pad, the cut-off scrap may be misrecognized as a probe needle mark of the probe. As described above, the image of the electrode pad may include various shapes of marks. Thus, it is difficult to accurately determine if these marks are actually probe needle marks. Further, even though these marks are actually probe needle marks, it is difficult to accurately determine if they are appropriate as needle marks.